Ignition system with magnetic pulse generating means



NOV. 23, 1965 KQNQPA I 2 9 IGNITION SYSTEM WITH MAGNETIC PULSE GENERATING MEANS Filed April 5, 1962 X TIME INVENTOR. B A] Richard 1. Kano 0a BY W 71 9. 6

H16 APTTORNEY United States Patent Ofifice 3,219,878 Patented Nov. 23, 1965 IGNITION SYSTEM WITH MAGNETIC PULSE GENERATING MEANS Richard L. Konopa, Anderson, Ind., assignor to General Motors Corporation, Detroit, Mich., a corporation of Delaware Filed Apr. 5, 1962, Ser. No. 185,291 6 Claims. (Cl. 315209) This invention relates to ignition systems for internal combustion engines and more particularly to a breakerless ignition system wherein a semiconductor such as a transistor controls the current flow through the primary winding of an ignition coil.

The present invention is directed to an ignition system for an internal combustion engine wherein a semiconductor such as a transistor controls the current flow through the primary winding of an ignition coil and wherein the semiconductor is turned on and olf by a pulse generating means driven by the engine. In this type of system, the pulse generating means develops pulses of voltage which control the on and off time of the transistor to therefore periodically interrupt the current flow through the primary winding of the ignition coil. One of the problems encountered in this type of system is to maintain the transistor switched off for a sufficient period of time to permit a large voltage to be induced in the secondary winding. It accordingly is one of the objects of this invention to provide a breakerless transistor ignition wherein the time that the transistor is turned off is increased as compared to heretofore known breakerless transistor ignition systems.

A more specific object of this invention is to provide a breakerless transistor ignition system wherein the turning on and turning ofi of the transistor that controls primary winding current is controlled by a pair of pick-up coils which have overlapping voltage output wave forms that maintain the transistor off for a period of time corresponding to the period where the voltage pulses overlap.

Another object of this invention is to provide a breakerless transistor ignition system wherein a semiconductor such as a transistor controls current flow through the primary winding of an ignition coil and wherein this transistor has its conductivity controlled by a pulse generating means that includes a plurality of pick-up coils.

Further objects and advantages of the present invention will be apparent from the following description, reference being had to the accompanying drawings wherein preferred embodiments of the present invention are clearly shown.

In the drawings:

FIGURE 1 is a schematic circuit diagram of an ignition system made in accordance with this invention.

FIGURE 2 is a top view of a magnetic voltage pulse generating means that controls the conductivity of the transistors shown in FIGURE 1.

FIGURE 3 is a sectional view of the voltage pulse generating unit taken along line 3-3 of FIGURE 2.

FIGURE 4 are curves of voltages generated in the pick-up coils of the magnetic voltage pulse generating means shown in FIGURES 2 and 3.

Referring now to the drawings and more particularly I to FIGURE 1, the reference number designates a source of direct current power for an ignition system which on a motor vehicle may be a storage battery. In motor vehicle installations, a generator charges the storage battery and supplies ignition power when the engine is running. One side of the battery 10 is grounded and the opposite side thereof is connected with an ignition switch 12. The opposite side of ignition switch 12 is connected with a lead wire 14.

The ignition system includes an ignition coil 16 having a primary winding 18 and a secondary winding 20. The primary and secondary windings are connected together at junction 22 and this junction is grounded as shown. One side of the secondary winding 20 is connected with lead wire 24 which in turn is electrically connected with a rotor contact 26 of a spark distributing device 28. The spark distributing device 28 includes the fixed contacts or electrodes 30 which are electrically connected with the lead wires 32. The lead wires 32 are connected respectively with the spark plugs 34 on the internal combustion engine 36. The opposite side of the spark plugs 34 are grounded as shown. The engine is shown as a four cylinder engine having four spark plugs, but it will be apparent to those skilled in the art that the system of this invention will have equal application to engines having a number of cylinders other than four.

The primary winding 18 of the ignition coil 16 is connected in series with a resistor 38 and this resistor is connected in series with a circuit element or three terminal semiconductor switch means which in this case takes the form of a PNP transistor 40 having emitter, collector and base electrodes. The current carrying terminals of the semiconductor switch means 40 are the emitter and collector electrodes while the control terminal is the base electrode. It is seen that the collector electrode of transistor 40 is connected with the resistor 38 whereas the emitter electrode of transistor 40 is connected with lead wire 14. The base electrode of transistor 40 is connected with a junction 42 via the lead wire 44.

The junction 42 is connected with the collector electrode of a PNP transistor 46. The emitter electrode of transistor 46 is connected with lead wire 14. Connected between the junction 42 and ground is a resistor 47.

The emitter and base electrodes of transistor 46 are connected by pick-up coils 48 and 50. These pick-up coils 48 and 50 have voltages induced therein as a magnetic rotor 52 rotates. The rotor 52 is driven by the engine 36 as is the rotor contact 26 of the spark distributor 28 as is depicted by the dotted lines of FIGURE 1.

Referring now more particularly to FIGURES 2 and 3, it is seen that the pick-up coil 50 is wound on one leg of U-shaped member 54 which is formed of magnetic material. In a similar fashion, the coil winding or pick-up coil 48 is wound on a U-shaped member 56 which is likewise formed of magnetic material. The rotor 52 as seen in FIGURES 2 and 3 comprises a pair of pole pieces 58 and 60 which are secured to a permanent magnet 62 and to a shaft 64 which drives the rotor 52. The pole pieces 58 and 60 are formed of magnetic material. The shaft 64 may be formed of stainless steel or may be fitted with a non-magnetic insert to magnetically isolate it from the permanent magnet and pole pieces. The pole piece 58 has four projecting teeth 58a which swing past one end of the U-shaped members 54 and 56 when the rotor 52 is rotating. The pole piece 60 is formed with teeth 6011 which are exactly aligned with the teeth 58a. It is seen from FIGURE 3, that as the rotor 52 rotates, the projecting teeth 58a and 60a pass by the ends or tips of the U-shaped members 54 and 56.

The permanent magnet 62 may be of the ferrite type or any other type and is axially magnetized so that the pole pieces 58 and 60 have different magnetic polarities. The U-shaped magnetic members 54 and 56 and the coils that they carry are fixed relative to the rotor 52 and can be secured to a suitable housing 61 formed of a nonmagnetic material such as die cast aluminum. It is also possible to secure the U-shaped members 54 and 56 to a rotatable breaker plate that will be adjusted by vacuum apparatus. In any event, the U-shaped members 54 and 56 and their attached coils are fixed a predetermined circumferential distance from each other regardless of what they are fastened to.

It is to be pointed out that the circumferential spacing between U-shaped members 54 and 56 is greater than the circumferential spacing of the teeth on the pole pieces 58 and 60. It thus is seen from FIGURE 2 that the radially extending teeth 58a are spaced 90 from each other whereas the ends of the U-shaped members 54 and 56 are circumferentially spaced a distance somewhat greater than 90. Where the rotor 52 rotates clockwise in FIGURE 2, it can be seen that one pair of teeth 58a and 60a will become aligned with the U-shaped member 56 before another pair of teeth 53a and 60a become aligned with the U-shaped member 54.

The voltage output of the pick-up coils 48 and 50 is depicted in FIGURE 4 which illustrates the voltage output as a function of time or rotor position. When a pair of teeth 58:: and 64a approach the U-shaped member 56,

a voltage m-n is induced in coil winding 48 which begins at point A. As the teeth 58a and 60a approach and then become aligned with the U-shaped member 56, a voltage wave form is developed which goes to a maximum in the negative direction at point B and then returns to point C when the teeth 58a and 60a are exactly aligned with the U-shaped member 56. As the teeth 58a and 60a now move out of alignment with the U-shaped member 56, a voltage of induction is developed which is in a reverse direction and which goes from point C through point D and then decays to point E on the solid line curve shown in FIGURE 4.

As soon as a pair of teeth 58a and 60a move out of alignment with the U-shaped member 56, a second pair of teeth 58a and 60a will be approaching the U-shaped member 54 and a voltage nm will be induced in the pick-up coil 59 which is depicted in the dotted lines of FIGURE 4. This voltage is the same as voltage mn but has a reverse polarity because of a reversal in connection of its output leads. This voltage n-m starts at point F, moves to a maximum in a positive direction at point G, then moves to Zero at point H, to a maximum in a negative direction at point I and then decays substantially to zero at point K. It is noted that the curves of voltages developed in pick-up coils 48 and 5t) overlap so that as the voltage in coil winding 58 is decaying from D to E a voltage is being developed at the same time in the coil winding 50 from points F to G. When the teeth 58a and 60a are out of alignment with both U-shaped members 54 and 56, there is no voltage developed in either coil winding 48 or 50'.

When it is desired to set the ignition system of this I invention into operation, the ignition switch 12 is closed. With the engine 36 either being cranked or in a running condition, the rotor 52 and the rotor contact 26 are driven by the engine. This causes pulses of voltage to be induced in the coil windings 48 and 5%) having the wave forms illustrated in FIGURE 4.

When the ignition switch 12 is closed and no voltage is induced in either coil winding 48 or 50, the transistor 40 will be conductive in its emitter-collector circuit so that current flows from lead wire 14, through the emittercollector circuit of transistor 40, through resistor 38 and through the primary winding 18 to ground. Transistor 40 is now conductive in its emitter-collector circuit because it has a path for base current which is through lead wire 44, junction 42 and the resistor 47 to ground.

With the rotor 52 rotating, a pulse of voltage shown between points A and B in the curve of FIGURE 4 will be induced in the coil winding 48. The coil winding 48 is so connected with the emitter and base electrodes of transistor 46 that this pulse of voltage will drive the base electrode of transistor 46 more positive than the emitter electrode so that the transistor 46 remains nonconductive. The junction 42 now has a potential which is essentially ground potential and the transistor 40 therefore remains conductive in its emitter-collector circuit. As the teeth 58a and 60a pass by the U-shaped member 56, the voltage curve moves from point C to point B as seen in FIG- URE 4. This will cause the base electrode of transistor 46 to become negative with respect to the emitter electrode and the transistor 46 now will begin to conduct current between its emitter and collector electrodes. With transistor 46 conductive between its emitter and collector electrodes, the junction 42 takes a potential which is substantially equal to the potential of lead wire 14. This then means that there is substantially no difference in potential between the emitter and base electrodes of transistor 40 so that it turns oif in its emitter-collector circuit. This interrupts the current flow to the primary winding 18 and as a result of this, a large voltage is induced in the secondary winding 20 which is applied to one of the spark plugs through the rotor contact 26 and one of the lead wires 32.

The transistor 46 remains conductive after a pair of teeth 58a and 60a leave the U-shaped member 56 since another pair of teeth 58a and 60a swing past the U-shaped member 54. A voltage nm then is induced in the coil winding St) which is shown in dotted lines in FIGURE 4. The output leads of coil winding 50 are connected in a reverse manner with the emitter and base electrodes of transistor 46 as compared to the connection of coil winding 48 with these electrodes. In other words, point 12 of coil Winding 48 is connected with the base electrode of transistor 46 whereas point m of coil winding 50 is connected to the same base electrode. Points 11 on the two coil windings are identical physical points on the coil windings, that is, they are at the same point on a coil winding relative to the magnetic circuit for the coil winding. The same is true of corresponding point m. Thus, as the voltage developed in pick-up coil 50 goes from points F to G, it drives the emitter electrode of transistor 46 positive with respect to the base electrode of this transistor so that the transistor remains turned on and thus keeps the transistor 40 turned off in its emitter to collector circuit. The voltage developed in the coil winding or pick-up coil 50 thus prolongs the time that the transistor 40 is turned off so that the circuit for the primary winding 18 is interrupted for a sufiicient length of time to cause a high voltage to be induced in the secondary winding 20 and a firing of one of the spark plugs 34.

When point H is reached on the curves of FIGURE 4, the transistor 46 is turned off and the transistor 40 once more resumes conduction in its emitter-collector circuit. When no voltage is induced in either coil winding 48 or 50, it is seen that the emitter and base electrodes of transistor 46 are connected to substantially the same potential so that the transistor 46 is turned off and the transistor 40 remains on. The transistor 40 is thus turned on in its emitter-collector circuit for a greater time than it is turned off during one revolution of the rotor 52 and will be turned on at four separate time intervals separated by four shorter time intervals Where it is turned off. The time of turn-off is prolonged with the system of this invention since the voltage wave forms developed by the pick-up coils 48 and 50 overlap as is clearly apparent from FIGURE 4. This insures that the current flow through the primary winding 18 of ignition coil 16 will be interrupted for a sufificient length of time to cause a high voltage to be induced in the secondary winding 20 and a good firing of the spark plugs 34.

While the embodiments of the present invention as herein disclosed constitute preferred forms, it is to be understood that other forms might be adopted.

What is claimed is as follows:

1. An ignition system for an internal combustion engine comprising, a source of direct current voltage, an ignition coil having a primary winding and a secondary winding, a circuit element having a pair of current carrying term nals and a GQntrol terminal, means connecting the 3 current carrying terminals of said circuit element in series with said primary winding and across said source of direct current voltage, voltage pulse generating means including a pair of oppositely poled coils connected in electrical parallel relationship with each other and a magnetic means adapted to be driven in synchronism with said engine positioned in cooperative relationship with said coils for producing spaced, discrete pairs of alternating current pulses, the pulses of each pair being shifted to partially overlap in only one polarity and means for connecting said coils across said control terminal and one of said current carrying terminals of said circuit element.

2. An ignition system for an internal combustion engine comprising, a source of direct current voltage, an ignition coil having a primary winding and a secondary winding, a three terminal semiconductor switch means having a pair of current carrying terminals and a control terminal, an energizing circuit for said primary winding including the current carrying terminals of said semiconductor switch means connected in series therewith, voltage pulse generating means including a pair of oppositely poled coils connected in electrical parallel relationship with each other and a magnetic means adapted to be driven in synchronism with said engine positioned in cooperative relationship with said coils for producing spaced, discrete pairs of alternating current pulses, the pulses of each pair being shifted to partially overlap in only one polarity and means for connecting said coils across said control terminal and one of said current carrying terminals of said semiconductor switch means.

3. The system according to claim 2 where the three terminal semiconductor switch means is a transistor.

4. An ignition system for an internal combustion engine comprising, a source of direct current voltage, an ignition coil having a primary winding and a secondary winding, a three terminal semiconductor switch means having a pair of current carrying terminals and a control terminal, an energizing circuit for said primary winding including the current carrying terminals of said semiconductor switch means connected in series therewith, voltage pulse generating means including first and second circumferentially spaced oppositely poled coil windings and a rotor member adapted to be driven in timed relation with said engine having circumferentially spaced teeth of magnetic material, the spacing of said teeth on said rotor member being less than the circumferential spacing of said coil windings, and means connecting said coil windings in parallel and in controlling relationship with the control terminal and one of said current carrying terminals of said semiconductor switch means.

5. An ignition system for an internal combustion engine comprising, a source of direct current voltage, an ignition coil having a primary winding and a secondary winding, a first transistor having emitter, collector and base electrodes, an energizing circuit for the primary winding of said ignition coil connected with said voltage source and including the emitter-collector circuit of said first transistor in series, a second transistor having emitter, collector and base electrodes, means connecting the emitter-collec tor circuit of said second transistor across said voltage source, means connecting the base electrode of said first transistor with the collector electrode of said second transistor, voltage pulse generating means including a pair of oppositely poled coils connected in electrical parallel relationship with each other and a magnetic means adapted to be driven in synchronism with said engine positioned in cooperative relationship with said coils for producing spaced, discrete pairs of alternating current pulses, the pulses of each pair being shifted to partially overlap in only one polarity and means for connecting said coils across the emitter and base electrodes of said second transistor.

6. An ignition system for an internal combustion engine comprising, an ignition coil having a primary winding and a secondary winding, a source of direct current voltage, a first normally conducting transistor having emitter, collector and base electrodes, means connecting the emittercollector circuit of said first transistor in series with said voltage source and the primary winding of said ignition coil, a second normally not conducting transistor having emitter, collector and base electrodes, means connecting the emitter-collector circuit of said second transistor across said voltage source in such a manner as to be forward poled, means connecting the base electrode of said first transistor whereby said first transistor is rendered not conducting while said second transistor is conducting, with the collector electrode of said second transistor, voltage pulse generating means comprising a pair of oppositely poled coils connected in electrical parallel relationship with each other and a rotor member having equiangularly spaced teeth of magnetic material about its circumference adapted to be rotated about an axis in timed relation with said engine, said coils being asymmetrically circumferentially disposed about said axis adjacent said teeth and having an angular displacement between adjacent coils greater than the angular displacement between adjacent teeth and means for connecting said coils across said emitter and base electrodes of said second transistor for controlling the period during which said second transistor is conducting.

References Cited by the Examiner UNITED STATES PATENTS 2,071,573 2/1937 Randolph ct .al. 315\218 X 2,120,109 6/1938 Merrill 310-111 X 2,602,149 7/1952 Burnelle et a1. 315209 2,787,649 4/1957 Ballard et a1 123-148 2,940,013 6/1960 Cook 315-(209 2,953,719 9/1960 Guiot 315--209 3,072,823 1/1963 Kirk 315205 3,087,001 4/1963 Short et a1 315209 DAVID J. GALVIN, Primary Examiner.

JAMES D. KALLAM, Examiner. 

1. AN IGNITION SYSTEM FOR AN INTERNAL COMBUSTION ENGINE COMPRISING, A SOURCE OF DIRECT CURRENT VOLTAGE, AN IGNITION COIL HAVING A PRIMARY WINDING AND A SECONDARY WINDING, A CIRCUIT ELEMENT HAVING A PAIR OF CURRENT CARRYING TERMINALS AND A CONTROL TERMINAL, MEANS CONNECTING THE CURRENT CARRYING TERMINALS OF SAID CIRCUIT ELEMENT IN SERIES WITH SAID PRIMARY WINDING AND ACROSS SAID SOURCE OF DIRECT CURRENT VOLTAGE, VOLTAGE PULSE GENERATING MEANS INCLUDING A PAIR OF OPPOSITELY POLED COILS CONNECTED IN ELECTRICAL PARALLEL RELATIONSHIP WITH EACH OTHER AND A MAGNETIC MEANS ADAPTED TO BE DRIVEN IN SYNCHRONISM WITH SAID ENGINE POSITIONED IN COOPERATIVE RELATIONSHIP WITH SAID COILS FOR PRODUCING SPACED, DISCRETE PAIRS OF ALTERNATING CURRENT PULSES, THE PULSES OF EACH PAIR BEING SHIFTED TO PARTIALLY OVERLAP IN ONLY ONE POLARITY AND MEANS FOR CONNECTING SAID COILS ACROSS SAID CONTROL TERMINAL AND ONE OF SAID CURRENT CARRYING TERMINALS OF SAID CIRCUIT ELEMENT. 